JP4990149B2 - Compression molding method and group of polymer material container preform - Google Patents

Description

  The present invention relates to compression molding of a preform (semi-finished) intended for continuous molding (typically by stretch blow molding) of a concave object (for example, a bottle or the like) using a polymer material. .

  A preform that maintains the shape of the final object unchanged, and a hollow body that is placed under the neck and is inflated until a larger capacity and correspondingly reduced thickness is envisaged. Consists of

  According to current technology, in order to form a preform, a polymeric material, which is first weighed according to pre-established values so that its mass completely and accurately fills the molding chamber of the mold, is a rigid metal matrix. Inserted into (steel), then punch pressure insertion into the same matrix cavity until the mold forming chamber is closed. That is, the chamber remains between the punch and the inner surface of the matrix when the mold is in the closed position and defines the shape of the preform. The punch defines the shape of the inner surface of the preform and the matrix has an inner surface that defines the shape of the outer surface of the preform.

  The technical problem inherent in the above-described technique and related to the mold is caused by the following facts. Upon insertion of the body of polymeric material to be inserted into the matrix (typically through separating the body from the continuous unformed mass supplied by the extrusion means), there is a (small) difference in value for a given value. Inevitably obtained. On the other hand, the volume of the (closed) chamber of the mold that must be completely and accurately filled with the polymeric material forming the preform is constant for each metal. Therefore, the technical problem of compensating for the inaccuracy of the mass of the weighing body with respect to the reference value arises.

  Eventually, it was proposed to compensate for the mass error (relative to the reference value) by concentrating it in the neck region of the preform through relative displacement between several parts of the mold. (See publication JP 10-337769).

  While this solution has the advantage of converting the mass error into a part that does not adversely affect the functionality or appearance of the bottle, it also has major drawbacks. In fact, mass error conversion occurs at the necked portion, causing slight deviations between the mold components and cooling of the material. This creates internal tension in the area where the error has been compensated, and unacceptable damage such as breakage or cracking when mechanical stress is applied to the neck in subsequent steps, such as bottle cap tightening. It may cause

  Furthermore, for example, if the error conversion is localized in a region where a circular groove exists on the collar of the neck as can be seen from the above Japanese literature, when the collar itself slides along a good conversion guide, Unnecessary friction may be generated in the groove, and it may become a place for collecting dirt.

  The object of the present invention is to solve the above technical problem by a valid and effective solution.

  Another object of the present invention is to increase the speed of solidification during preforming and subsequent solidification steps by simultaneously improving the efficiency of heat exchange between the mold and the preform.

  These and other objects are achieved by the invention as characterized in the claims.

  The method according to the present invention predicts the distribution of the mass error of the weighing body relative to the reference value into the hollow body, and during the formation of the preform, the hollow body is expected to undergo thermal deformation until the hollow body reaches its final shape. Is done.

  When the preform is subsequently cooled, the internal tension may increase due to the mass error of the weighing body being distributed throughout the hollow body. However, since this hollow body passes through a heating process that involves thermal deformation until reaching its final shape, all possible internal tensions are removed to some extent. The same is true if the preform is kept cool without being cooled and deformed until it reaches its final shape.

  According to a preferred embodiment, the compensation of the error of the weighing body in the preform mold can be performed by causing an elastic deformation at least at one location on the inner surface of the matrix. In such a case, the mass reference value of the weighing body is calculated with the mold molding chamber empty (ie, the condition in which the mold is not in operation), and has a mass that always fills the volume. The error is considered as an excess of polymeric material relative to the volume of the chamber itself. In the subsequent preform molding process, at least a portion of the inner surface of the matrix is elastically deformed with respect to the “unfilled” shape due to the excess of polymeric material, resulting in the thickness of the hollow body. Will increase beyond the “unfilled” thickness to absorb weighing errors.

  The excess of the polymer material is therefore distributed uniformly and uniformly in the hollow body of the preform, so that the thickness error can be kept to a very small value (on the order of a few hundredths of mm).

  After forming the preform, when the preform and especially its hollow body part is deformed to reach the expected final shape, the thickness error of the hollow body is distributed over a larger area, so that The amount of error is small. Actually, the initial error of the mass of the measuring body is finally reduced to a level that cannot be detected by a general measuring device as an error in the state of the bottle.

  A portion of the matrix is designed to have a strength that can withstand elastic deformation to the extent that the polymeric material is deformed under pressure substantially equal to a pre-established design value in the final molding process.

  In the following, the invention will be described by way of example with reference to the accompanying drawings which show several embodiments of a mold for preform molding.

  An example of a preform obtained by the present invention is shown in FIG. This preform 9 is for realizing a bottle made of a thermoplastic resin PET (typically by stretch blow molding), and a neck 91 having a final predicted shape of the bottle and a container having the same shape in the bottle realizing process. It consists of a hollow body 92 intended to form a body. In general, the neck 91 is provided with a protruding portion that defines a thread 93 that protrudes radially outward to receive, for example, a normal screw cap. On the other hand, the hollow body 92 is usually substantially cylindrical (having a continuous outer surface slightly tapered toward the bottom for convenience of removal), and its lower end is generally spherical. A cap is attached. In particular, the hollow body 92 is comprised of a substantially cylindrical side wall 92a and a bottom wall 92b, typically in the shape of a cap.

  The preform 9 has a closed cavity hollow body (female mold part) filled with a pasty polymer material (especially thermoplastic resin) 8 having a certain viscosity whose mass is measured according to a reference value. It is obtained by a compression molding process in which a punch 11 (male part of a mold) is press-fitted into the inside.

  A molding machine using a mold according to the present invention is typically a turntable type that rotates continuously, but is not limited to this, and typically operates a plurality of the same molding groups in order. This type is not limited to this.

  The mold shown is only very general according to the present invention. On the other hand, the machine is not shown, but it may be a traditional one.

  The mold according to the present invention is composed of a matrix and a punch 11. By combining the punch 11 and the matrix cavity, a molding chamber 7 is formed which gives the preform 9 the desired shape. The matrix cavities form the outer surface of the preform, while the outer surface of the punch 11 forms the inner surface of the preform 9.

According to the illustrated embodiment, the mold matrix is formed by an upper matrix portion 20 and a lower matrix portion 30;
The upper matrix portion 20 is adapted to form the outer surface of the upper neck 91 of the preform and is divided into at least two sectors spaced apart from each other to enable the preform 9 to be drawn. Have The lower matrix portion 30 is aligned to form the outer surface of the preform hollow body 92.

  The upper and lower matrix portions 20 and 30 may be separated from each other in the filling step of the weighing body 8, and the weighing body 8 is inserted into the cavity of only the lower matrix portion 30. The inner surface areas of the upper and lower matrix portions 20, 30 are aligned to form the entire cavity of the matrix when operating in conjunction with each other.

  Alternatively, the two molds can remain combined during the metered material filling phase.

  According to the present invention, the lower matrix portion 30 is a non-deformable support 40 containing at least one deformable wall 31 realized by steel (or an equivalent material), and the inner surface of the deformable wall. Defines at least part of the inner surface of the lower matrix part, and at least partially changes elastically under the pressure of the polymeric material in the final molding step of the preform, thus changing the thickness of the hollow body A support 40 in the form of a thin film having a relatively thin thickness that can be increased, in particular increased. The wall 31 is deformed mainly by bending along a general axial plane together with deformation due to attractive force, but the wall thickness is not greatly changed.

  According to the first embodiment shown in FIG. 1, the lower matrix portion 30 is a portion 38 having a cylindrical shape, specifically a cylindrical shape, which defines the deformable wall 31, and an inner surface 31 ′ thereof is At least partially (specifically, almost completely as shown) includes a portion 38 that provides the shape of the outer surface of the side wall 92a of the hollow body 92, the wall 31 being elastically under the pressure of the polymeric material. It has a relatively thin thickness that can be deformed.

  The deformable wall 31 is housed in a coaxial cavity 36 made in the support 40 with its inner surface placed away from the surface of the wall 31 so as to deform radially without being disturbed by the support 40 itself. Enclose in detail.

  The deformable wall 31 includes an extended portion that defines a circular band 32 near the upper end and a second extended portion near the lower end that defines a second circular band 33. The circular bands 32 and 33 have outer cylindrical surface surfaces 32 'and 33' that contact corresponding pedestals 34 and 35 formed in the coaxial cavity 36 of the support 40, respectively. This defines two circular radially adjacent areas to the wall 31 that also serve for centering the wall 31. Said surfaces 32 'and 33' are completely cylindrical so that contact only works in the radial direction. The upper band 32 also includes a shoulder 32 a that is axially blocked by a pedestal 34.

  Along the general axial plane, the deformable wall 31 includes two ends defined by circular bands 32 and 33 from one and the other with respect to the axis. These form adjacent and central positions that prevent radial displacement, have a relatively thin thickness compared to the axial length in a single layer with two ends in a thin layer, and in the radial direction Elastically bends to form an arc in the axial plane.

  Specifically, the support body 40 includes a first cylindrical body 41, an outer case 43, and a second upper body 42 that is integrally coupled to the first cylindrical body 41 by an upper sealing case 44.

  An undeformable central structure 45 whose upper surface 45 ′ defines the outer surface of the bottom wall 92 b ′ of the hollow body 92 is placed inside the first unit 41. The lower band 33 is also blocked in the axial direction by the respective pedestals 35. More specifically, the lower shoulder is foreseen to be near the lower end of the inner wall 31 that contacts the upper end of the central structure 45 to ensure continuity between the wall 31 and the upper surface 45 ′ of the central body 45. The

  Cavity 36 is connected through conduit 46 and others (not shown) to means for introducing, circulating and exhausting coolant capable of removing heat from the preform in the preform temperature adjustment step (cooling). The The deformable wall 31 itself serves this conclusion in a unique way due to the fact that it has a relatively thin thickness through which heat conduction is highly advantageous.

  In addition, the deformable wall 31 may have various reliefs 37 that define heat exchange elements along its outer surface. These elements are intermittent in the circumferential direction in order not to disturb the elastic radial expansion of the deformable wall 31 in the molding process.

  In the embodiment shown in FIGS. 1A and 1B, the relief 37 has the shape of a fin protruding in the radial direction and extending a certain distance in the axial direction. These reliefs are staggered between one row and the other to achieve maximum turbulence in the coolant passage and maximize heat exchange with the wall 31. .

  In the embodiment shown in FIG. 1C, the relief 37 has a shape on a ring located on a plane orthogonal to the axis of the wall 31, but the ribs do not harden and prevent the wall 31 from radially expanding. There is a cut.

  Furthermore, conduits (not shown in the figure) suitable for cooling and / or temperature adjusting the central body 45 and cooling and / or temperature adjusting the lower end of the preform through such central body can be foreseen.

  The punch 11 is integrally fixed to the upper body 10 which forms a single body together, and forms a lower end portion of the punch 11 to give a shape to the inner surface of the preform. More specifically, the upper body 10 includes a shoulder that is adapted to abut the upper end 23 of the upper matrix portion 20, and a lower portion 10 "that is joined to the punch 11 itself within its lower compartment.

  The upper surface 91b of the upper edge of the neck 91 of the preform 9 is a narrow, downwardly rotating, partly ending in a substantially horizontal tangent surface and defining the upper boundary of the inner surface of the upper matrix part 20. The upper surface 21b, part of which is rotating downwards narrowly, ending at a substantially horizontal tangential surface defining the upper boundary of the outer surface of the punch at the boundary with the lower end of the lower part 10 "of the upper body 10 And upper surface 12b (see FIG. 1D).

  When both the top surfaces 12b and 21b are aligned, the mold is in a closed position; that is, the punch 11 and the matrices 20 and 30 are connected to each other, and the inner surface of the matrix portions 20 and 30 therein and the surface of the punch 11 The mold cavity defines the mold chamber 7 so that the shape of the preform is defined therebetween.

  In operation, the matrix of the polymeric material weighing body 8 whose mass has been weighed according to the reference value takes into account the errors that inevitably exist in the weighing of the weighing body in the cavity, The volume of the molding chamber 7 of the mold calculated in the above is added so that the measuring body 8 itself always fills completely (see FIG. 2A), and the error is higher than the volume of the chamber itself. First of all, surplus is expected.

  Subsequently, while lower matrix 30 is raised by the lower device (not shown in the figure), upper body 10 carrying punch 11 and the punch itself are kept stationary and brought closer to each other.

  2A to 2D, the horizontal reference line is represented by X and is constant and crosses the lower abutting shoulder of the upper part 10 'of the body 10.

  However, it is clear that what is important here is a movement involving mutual approach: this movement or the upper body 10 is moved downward, if possible, the upward movement of the lower device carrying the matrix. Obtained by moving with.

  First (FIG. 2B), the punch 11 starts to enter the cavity of the lower matrix portion 30 and gradually begins to deform the measuring body 8.

  Subsequently, the upper end of the lower matrix portion 30 and the lower end of the upper matrix 20 are brought together (position shown in FIG. 2C), and the punch 11 continues to advance in the cavity of the matrix and continues to deform the measuring body 8. The section forming the upper matrix part 20 is radially closed by an upper annular body (known type) associated with the punch 11 and moves in a direction perpendicular thereto, the lower end of which is a concave half-cone. It has a surface 14a that joins the outer and upper side surfaces of the complementary, also semi-conical upper matrix part 20.

  Subsequently, the punch 11 continues intrusion until the two surfaces 12b and 21b come into contact (position shown in FIG. 2D) and the mold is completely closed (always following the movement above the lower device carrying the matrix). )

  During this preform final molding step, the metered polymeric material fills the chamber 7 before the molding cavity 7 is still closed, while the deformable wall 31 is not at least appreciably deformed. Appropriate high pressure values are achieved that are within the range of design values expected at the end of molding. The punch then penetrates further into the matrix cavity until the mold is closed, but the volume of polymeric material is excessive compared to the capacity of the cavity 7 and is therefore pushed by the pressure generated by the punch penetration. The material is free to bend in its inclusive axial cross section and elastically moves the elastic wall 31 free from any abutment provided by the bands 32 and 33 radially outward until the excess volume is absorbed. Deform.

  The elastic deformation that the deformable wall 31 undergoes is of a type in which the cross section in the inclusive axial direction is deflected, the displacement in the axial central region of the wall itself is deflected outward, and the displacement is an excess of the measuring body. It is just volume. On the other hand, in the case of the cylindrical mold according to the first embodiment (FIG. 1A), the deformation in the inclusive cross-sectional direction that the elastic wall 31 receives is that the diameter of the cylindrical wall itself increases and reaches the maximum value in the central region of the shaft. is there. Accordingly, the cylindrical wall 31 is subjected to stress composed of both elastic bending and tensile force. 1 and 1A is distributed in the thickness of the side wall 92a of the hollow body 92 and increases regularly, reaching a maximum value in the middle region, but the band 32 and In 33, since it hardly deforms, its thickness hardly changes.

  Elastic deformation does not occur and does not change in other parts of the matrix, in particular the upper part 20 which gives shape to the neck 91.

  Therefore, the error of the weighed mass relative to the reference value is distributed in the preform part located in the deformable wall 31, ie in the hollow body 92.

  The reference value of the mass of the weighing body 8 is calculated taking into account both the error in forming the weighing body 8 and the volume reduction that occurs during the cooling of the preform during molding, and the molding chamber 7 is completely filled, In the final step of molding, a pressure of an appropriate design value (several hundred bar) is applied to the mass of the polymer material. In particular, the above reference value is such that the polymeric material of the metering body is always larger than the volume of the molding chamber, so that the deformable wall 7 always undergoes a somewhat significant amount of deformation. Is expected.

  The deformable wall 31 absorbs the excess volume of the weighing body and at the same time provides sufficient resistance to elastic deformation only by the effect of its own structural properties (without being influenced by external means and actions). This allows the polymeric material of the metering body to achieve the above-mentioned design value for pressure in the final molding step and also to have structural properties (especially material and length) that allow the wall 31 to deform after the molding chamber is completely filled. Designed to have a thickness distribution in the direction).

  Therefore, the deformable wall 31 must be dimensioned in relation to a plurality of parameters including the forming force that acts and the dimensional error of the metering body. For example, in the case of a preform having a mass of 24 grams and an overall axial length of 100 mm, in the lower matrix portion 30, the deformable wall 31 has a low carbon value and a high value of Mo, Ni, Co, and Ti. Steel is used, and the thickness of the central part sandwiched between the two contact parts defined by the bands 32 and 33 is about 2.5 mm. Assuming that the mass error of the measuring body 8 is expected to be 1% at the maximum during the test operation, the deformation of the wall 31 in the radial direction was on the order of 0.02 to 0.05 mm.

  In the second embodiment depicted in FIG. 3, the deformable wall 31 has an inner surface 38 ′ that defines at least a portion of the outer surface of the side wall of the hollow body 92 (and in particular, substantially all as illustrated). A cylindrical portion (substantially equal to the entire wall 31 of the first embodiment), in particular, a substantially cylindrical side portion 38, and a side portion 38, which are integrally joined, and the inner surface 39 'is hollow. It includes a cap-shaped bottom 39 that defines the outer surface of the low wall 92b of the body 92.

  This deformable wall 31 has a relatively thin thickness almost entirely, and when compressed by the polymeric material, it deforms elastically at both the side 38 and the bottom 39.

  The two annular bands 32 and 33 are disposed at the upper end and the lower end of the side wall 38, respectively.

  In this case, the coaxial cavity 36 also surrounds the bottom 39 of the wall 31.

  The lower sheet 35 that abuts the lower band 33 defines a cylindrical abutment surface and allows a limited number of radial and axial directions to allow communication between the upper and lower portions of the cavity 36. Fins 48 are provided.

  The contact between the band 33 and the corresponding contact sheet 35 enables the band itself to slide in the axial direction, so that the elastic deformation of the deformable wall 31 in the axial direction is not hindered.

  Therefore, in this second embodiment as well as in the first embodiment, the deformable wall 31 does not impede radial displacement from one side to the opposite side of the shaft along the holographic shaft cross section. Two ends defined by the annular bands 32 and 33 forming the contact part, and a long and relatively thin thickness in the axial direction, are integral with the two ends, and are freely elastic in the radial direction It includes a central thin plate that can bend flexibly and forms an arc on the axial surface. In addition, it has two ends along the inclusive axial cross section, defined by an annular band 33 and a central portion that is relatively thin with respect to length and can be elastically deflected axially. A deformable bottom 39 is also included.

  The cavity 36 circulates a cooling fluid capable of removing heat from the preform in a preform thermal conditioning step (cooling) through a bottom opening 49 opened in the central body 45b and other conduits not shown. Connected to a suitable means.

  In operation, this embodiment is such that the pressure exerted by the metering body 8 on the inner surface of the molding chamber 7 elastically deforms both the side 38 and the bottom 39 of the deformable wall 31 and therefore the weighing body error is reduced. This is different from the previous embodiment in that it is distributed not only to the side portion 92a of the hollow body 92 but also to the bottom portion 92b. Furthermore, the deformable wall 31 is also subjected to deflection and axial deformation.

  Also in the third embodiment depicted in FIG. 4, as in the second embodiment, the deformation wall 31 has a cylindrical shape (substantially equal to the entire wall 31 of the first embodiment), particularly substantially a cylinder. The shaped inner surface 38 ′ is at least partially joined to the side 38 defining the outer surface of the side wall 92 a of the hollow body 92, and the side 38, and the inner surface 39 ′ is the bottom of the hollow body 92. Also included is a cap-shaped bottom 39 that defines the outer surface of wall 92b. However, unlike the second embodiment, here, the two portions 38 and 39 are separated from each other, but it is expected that the respective inner surfaces will be continuous when they meet.

  The bottom annular band 33 is made at the upper annular boundary of the bottom 39, and correspondingly the two parts 38 and 39 are fixed to each other. The band 33 has a series of radial ribs 51 whose radial ends define a cylindrical surface that abuts a bottom sheet 35 which is also cylindrical.

  Again, as in the previous embodiment, the coaxial cavity 36 also surrounds the bottom 39 of the wall 31 and the bottom sheet 35, and the ribs 51 allow communication between the bottom of the cavity 36 and its top.

  In particular, there is a center 45 b inside the cylindrical body 41, and its upper surface is arranged at a distance from the lower surface of the bottom 39.

  The contact between the band 33 and each contact sheet 35 allows the band itself to slide in the axial direction, and does not prevent the elastic deformation of the deformable wall 31 in the axial direction.

  The cavity 36 passes through a bottom opening 49 opened in the central body 45b and other conduits (not shown) to supply cooling fluid that can remove heat from the preform in the preform thermal conditioning (cooling) step. Connected to a suitable means for circulating in the water. Below the cavity 36 and below the abutment rib 51 are a plurality of fins 53 projecting upward from the central body 45b, which are suitable for adjusting the direction of the flow of the cooling fluid, and for deforming the wall 31. Do not block or touch the wall. Also in the third embodiment, the measurement error of the polymer material is distributed to the bottom 92b in addition to the side 92a of the hollow body 92.

  Further, a plurality of conduits provided inside the support body 40, particularly the center body 45 b and the fins 53, crossing the rib 51 and the lower band 33 and reaching the interconnection between the lower end of the side wall 38 and the upper end of the bottom 39. 54 can also be expected.

  Said conduit 54 may conveniently be connected to a suction means for removing air bubbles in the mold cavity before and during the compression step of the metering body.

  Additionally or alternatively, the conduit 54 is used to inject air or heat conditioned fluid into the cavity prior to the mold opening step, which is advantageous for post-molding cooling and preform stripping. Any suitable means may be connected.

  The fourth embodiment (FIG. 6) is a modification of the first embodiment (FIG. 1 and FIG. 1A), mainly to increase the capacity of the matrix that receives the weighing body, in order to increase the capacity of the matrix PCT / IB2005 / 002303 ( The central body 45 has been modified in accordance with the teachings of the invention described in the same applicant's Italian Patent Application No. RE2004A000127 (which claims priority). In particular, the central body 45 includes a first component body 451 and a second component body 452 disposed centrally relative to the first component body, each having an inner surface 453 and 454, which are complementary. Aligned together in a symmetric fashion, the inner surface 45 'can be defined.

  The first component body 451 is integrally coupled to the remaining lower matrix portion 41, and particularly integrally coupled to the main body 41. The second component body 452 is located above the first component body 451 in an upper position where the inner surface 454 is aligned or substantially aligned with the inner surface 453 of the first component body 451 (in FIG. 6). And a rear position (indicated by a broken line in FIG. 6) where the inner surface 454 is arranged away from the inner surface 453 of the first component body 451 in order to increase the volume of the cavity below the matrix. it can. Finally, it is suitable for placing the second component body in the rear position in the step of filling the cavity of the lower matrix part 30 with the polymeric material, and in the molding step in the upper position. Driving means are expected (not shown in the drawing).

  In operation, the metering body is first made out of the mold and then inserted into the cavity of the lower matrix part, while the second component body 452 is in the rear position.

  The punch is then allowed to enter the matrix until the mold is closed in the same or similar manner as described above with reference to FIGS. 2A-2D, while the second component 452 remains in the rear position. It has been.

  Once the punch 11 is fully inserted into the matrix until the mold is closed (at this time the lower matrix 30 is joined to the upper 20 and the two surfaces 12b and 21b touch each other), the second component The body 452 is displaced upward until it reaches the upper position. This final step can be started after mold closure or shortly before.

  In this final step, the polymeric material is squeezed to completely fill the molding chamber and then deform the elastic wall 31, thereby increasing the thickness of the hollow body until the excess volume of the metering body is absorbed.

  The upper position need not be a position where the surface 454 of the second component body 452 exhibits accurate geometric continuity with the surface 453 of the other component body 451 (design “nominal position”), There are various ways to deviate from this position, depending on the mass error level of the weighing body. Therefore, this upper position may be below the “nominal position”.

  According to another embodiment (not shown in the figure), the deformable inner wall 31 includes only the bottom, so that the error of the weighing body is expected to be arranged only in the bottom 92b of the hollow body 92. The

  According to the invention, the molded preform is cooled and subsequently subjected to a deformation process by stretch blow molding, and the hollow body is heated again until it reaches the desired shape. Alternatively, the preform is stretch blow molded with the temperature of the hollow body still high enough to undergo a deformation process.

  According to the present invention, firstly, since the weighing error is distributed over a relatively wide area in a continuous manner, no trace remains on the appearance of the final container obtained at the end of the entire process; In fact, there is no size variation between one final container and another.

  Furthermore, after preforming, excess tension, which can occur when metering errors are distributed to the hollow body, is removed by subsequent heating of the hollow body; otherwise the temperature of the hollow body is sufficient In such a case, the tension is not even formed because the mass is kept high and the mass is kept in a viscous fluid state to some extent.

  In the fourth embodiment (FIG. 6), the volume of the cavity of the lower matrix part is increased in comparison with the volume of the conventional mold in the step of receiving the weighing body, and the mass or height of the acceptable material is increased. Yes. Furthermore, in addition to the compensation of the error obtained by the elastic deformation of the deformable wall 31, the upper position of the second component body 452 does not exactly match the nominal position, and even if it is away from this, the error of the weighing body can be reduced. Thanks to the fact that another compensation obtained by ensuring that at least a part is compensated, a relatively large error becomes acceptable.

Sectional drawing of 1st embodiment of the metal mold | die by this invention. The enlarged view of the center part of FIG. FIG. 3 is a perspective view of the deformable wall 31 of FIG. 1. FIG. 3 shows another embodiment of the deformable wall 31 of FIG. 1. FIG. 2 is an enlarged view of details of FIG. 1. The figure which showed in order the procedure which shape | molds a preform with the metal mold | die of FIG. The figure which showed in order the procedure which shape | molds a preform with the metal mold | die of FIG. The figure which showed in order the procedure which shape | molds a preform with the metal mold | die of FIG. The figure which showed in order the procedure which shape | molds a preform with the metal mold | die of FIG. Sectional drawing of 2nd embodiment of the metal mold | die by this invention. Sectional drawing of 3rd embodiment of the metal mold | die by this invention. The top view seen from the upper part of the bottom part 39 of FIG. The perspective view of an example of the preform obtained by the present invention. Sectional drawing of 4th embodiment of the metal mold | die by this invention.

Claims (21)

A method of making a concave object of a polymer material,
An upper neck portion, compression molding the preform and a hollow body which is joined to the neck portion, and extends the hollow body to increase its volume, and hot to corresponding reduction in the thickness treating deformation the hollow body continues to under the compression molding temperature, wherein the
Preform compression molding
A matrix comprising a first part (20) forming the outer surface of the upper neck (91) and a second matrix part (30) forming the outer surface of the hollow body (92) and having a deformable wall (31); Providing a mold having a punch to form the inner surface of the preform;
The calculated reference mass value of the weighing body is calculated so that the volume of the polymer material causes an excess error with respect to the mold molding chamber, and the weighing body made of the calculated polymer material is inserted into the matrix cavity. thing,
Reaches the mold closed position, and wherein in the final stage of insertion, to press insert the punch completely filled until hoax trix cavity a molding chamber of a polymeric material, a
The deformable wall (31) is elastically deformed by inserting a punch to absorb the error of the surplus volume of the measuring body, and the polymer material corresponding to the surplus volume of the measuring body is distributed along the entire surface of the hollow body. And increasing the thickness of the hollow body. After the forming of the preform, the hollow body is cooled, then method according to claim 1, characterized in that successively receiving the subsequent heating and deformation processing until the final product is formed.   In the molding of the preform, the outer peripheral side (38) of the deformable wall (31) having a tubular shape is elastically deformed, and the surplus of the polymer material is at least partly removed from the side wall (92a) of the hollow body (92). 2. The method according to claim 1, characterized in that the method is distributed.   In the last stage of punch insertion, the polymer material metering body completely fills the molding chamber (7) and the volume of excess polymer material pressed by the punch insertion determines the pressure value of the polymer material, 4. A method according to claim 3, characterized in that a value equal to a pre-established value is achieved by the resistance against elastic deformation caused by the deformable wall without any external means or action.   In preform molding, at least a portion of the inner surface of the matrix is elastically deformed relative to its “unloaded” position by extending the length of the hollow body to absorb excess polymeric material. The method according to claim 3. A mold for compression-molding a preform of a polymer material for molding a concave object,
The preform includes an upper neck portion having the same shape as the final product, and a hollow body joined to the neck portion,
In the compression molding step, a polymer material weighing body is inserted into the matrix cavity by using an excess volume of the polymer material relative to the volume of the mold molding chamber.
Pressure inserting a punch into the matrix cavity until the mold chamber is completely filled with polymeric material in the final stage of metering insertion,
The compression mold is
A matrix having a first portion (20) forming the outer surface of the neck portion (91) and a second matrix portion (30) forming the outer surface of the hollow body (92), and a punch forming the inner surface of the preform Have
The matrix comprises at least one deformable wall (31), the inner surface of the deformable wall (31) defining at least part of the inner surface of the matrix portion forming the hollow body (92) of the preform;
Said deformable wall (31), Chi also thin portion of the thickness,
The deformable wall (31) increases the thickness of the hollow body to absorb the error of the excess volume of the measuring body, and can be elastically deformed under the pressure of the polymer material generated by the insertion of the punch. A mold, characterized in that the elastic deformation of the deformable wall (31) can provide a total resistance against the elastic deformation without any external means or action.   Due to the structural features of the deformable wall (31), intervening external means or action so that the polymeric material reaches a pressure value equal to a predetermined pressure value at the final stage of the punch insertion. The mold according to claim 6, wherein the mold can be resisted against the elastic deformation without any.   7. Mold according to claim 6, characterized in that the deformable wall (31) is made of steel. The deformable wall (31) comprises a tubular outer peripheral side (38), the inner surface (38 ') of the tubular outer peripheral side (38) at least the outer surface of the side wall (92a) of the hollow body (92). The mold according to claim 6, wherein the mold is partially defined. 9. The deformable wall (31) comprises at least one end portion (33), the end portion (33) sliding axially on the abutment seat (35). The mold described. The deformable wall (31) comprises at least a tubular outer peripheral side (38), the portion (38) being arranged along the axial plane of the deformable wall (31), the deformable according to claim 9, characterized in that it comprises two end portions having an abutment for preventing displacement with respect to the radial direction of the wall (31), and a central portion which bends resiliently freely radius direction Mold.   A non-deformable central structure (45) defining an outer surface of the hollow body (92), the surface (45 ') of the central body (45) defining the outer surface of the bottom wall of the preform; A first stationary component (451) and a second movable component (452) having inner surfaces (453, 454) in which the body (45) is aligned in a complementary manner and together defines an inner surface (45 '). The second movable component (452) has an inner surface (454) aligned with an inner surface (453) of the first fixed component (451) with respect to the first fixed component (451), or Between an upper position that is placed in an aligned position and a retracted position whose inner surface (454) is placed away from the inner surface of the first stationary structure (451) and the volume of the cavity in the lower part of the matrix increases. The lower mat of the weighing body of the polymer material that can move There is provided operating means arranged to place the second movable structure (452) in the retracted position in the step of inserting the hook part (30) into the cavity and move it to the upper position in the forming step. The mold according to claim 9, wherein the mold is characterized in that   The deformable wall (31) comprises a bottom (39), the inner surface (39 ') of the bottom (39) at least partly defining the outer wall of the bottom wall (92b) of the hollow body (92). The mold according to claim 9, wherein   The deformable wall (31) comprises a circular band (32) at the upper end and a circular band (33) at the lower end, the circular band (32, 33) having a diameter relative to the deformable wall (31). The mold according to claim 9, wherein a direction contact region is formed. The contact between the lower band (33) and the respective contact seat (35) allows the band itself to slide in the axial direction and does not hinder the elastic deformation in the axial direction of the deformable wall (31). 15. A mold according to claim 14, characterized in that   The deformable wall (31) is enclosed in a coaxial cavity (36) formed in the support (40), the inner surface of the support is placed away from the outer surface of the wall (31), and the support (40) itself The mold according to claim 9, wherein the mold can be deformed without being obstructed by the mold.   Intermittently in the circumferential direction so that the deformable wall (31) does not interfere with the relief (37) defining the heat exchange element on the outer surface of the deformable wall (31); The mold according to claim 9, wherein the mold is provided.   A relief (37) is formed as an axially extending fin projecting radially and further in a cavity arranged between the inner surface of the second matrix part (30) and the outer surface of the variable wall (31) The mold according to claim 17, wherein the mold is alternately arranged between one row and the next row in order to realize turbulent flow in the passage of the cooling fluid that circulates.   The deformable wall (31) comprises a tubular outer peripheral side (38) and a bottom (39) which are separated from each other and are combined in any case to form a continuity of the respective inner surface. The mold according to claim 9, wherein   Having at least one conduit (54), said conduit (54) extending in correspondence with the surface of the interconnection between the lower end of the tubular peripheral side (38) and the upper end of the bottom (39), 20. The conduit (54) is connected to suction means adapted to exclude air present in the mold cavity before and during the compression stage of the metering body. The mold described.   Having at least one conduit (54) across the deformable wall (31), the interconnect (54) between the lower end of the side (38) and the upper end of the bottom (39) 20. A mold according to claim 19, wherein the mold extends corresponding to the surface.

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